1. Field of the Invention
The present invention is related generally to expert systems utilized with database systems, and more particularly, to expert systems and methods utilized within the data communication industry.
2. Description of Related Art
A communications network is a chain of terminals and computer ports or other facilities organized for simultaneous operation. The number of devices might be anywhere from two up to several hundred or even thousands. In general, communications networks are an extremely efficient way of using and sharing communications resources.
FIG. 1 depicts in block diagram form a typical network where a communications network user 110 communicates with communications network user 112 via a telephone line, utilizing modulator/demodulators (modems) 106 and 108, to convert the digital signals from the computer terminal 102 and 104 to corresponding analog signals suitable for transmission via the telephone line. In order to maximize the utilization of communications resources, more than two communication network users need to utilize a telephone line simultaneously. In order to do this, various communications techniques have evolved. One of the most common communications techniques utilized in a conventional network is to introduce a third entity, multiplexer (MUX) 202 and/or 204, into the communication network 214, as shown in block diagram form in FIG. 2.
The multiplexers 202, 204 are devices utilizing a technique whereby the simultaneous transmission of separate information is realized. As applied to communications networks, the term multiplexer refers to methods for sharing the network path which is usually a single cable of some kind, such as a telephone line.
Time-division multiplexing (TDM) is a common and useful multiplexing method. In time-division multiplexing, there is only one real channel which the users "take turns" using. There are many ways this "turn-taking" can be controlled. Typically in TDM, time is divided, with each segment of time being in effect a private "channel within a channel." As shown in FIG. 3 (where instead of two users we have four users), we can see that time division multiplexing would breakup the turn taking into brief predetermined lengths of time called time slots, (there are four time slots shown). Conventional TDM networks operate in the 1 kilobit per second (kbs) data rate range and up. Representative data rates include the Case DCX multiplexed network which operates, for example, between 1.2 and 64 kbs. Also representative of conventional TDM networks is the so-called T1 network, which operates at approximately 1.54 megabit per second data rate. Other representative examples include T2, T3 and T4 networks which typically operate in the higher megabit per second range. Note that these are representative examples of conventional TDM networks.
Time division multiplexing thus has become a widely used conventional communications network technique that allows the usage of a single resource for many users. However, TDM is physically limited by the amount of sampling or turn taking time into which a channel can be broken.
This limitation was overcome in yet another technique, which is commonly referred to as statistical time division multiplexing or STDM. In STDM, allocation of "turn taking" or sampling by communications network user 404 is based on a statistical sample 406 of the channel 402 in question as shown diagramatically in FIG. 4. The time slots 406 are allocated to communication network users 404 dynamically according to the level of digital data from each user 404. The statistical sampling and allocation of time slots 406 results in a many fold increase in the number of users 404 that can actively utilize any one communications channel 402 by maximising the available multiplexing time. Modern communications networks utilize STDM as part of the communications network topology to increase user 404 utilization and economies of scale.
As shown in block diagram form in FIG. 5, a multiplexer communication network 500 can comprise a number of multiplexers (which are contained in a node 506 and a feeder 508) interconnected by composite links 504. A composite link 504 is capable of carrying a number of communications simultaneously by multiplexing. When the connection between two end points (ends) 502 of the communication network 500 is realized by the communications network 500, the connection passes through a number of multiplexers (feeders 508/nodes 506) and composite links 504. As stated above, multiplexer function may be part of either a node 506 or feeder 508. The function of a node 506 is to switch communications traffic between a number of ends 502, such as computer ends 510 or terminals ends (not shown). The function of a feeder 508 is to concentrate the communications traffic from a number of ends 502 into single composite links 504, which traffic can then be fed into a node 506.
The nodes 506 and links 504 through which a "permanent" connection passes (not explicitly shown), and the channels used on those links 504, are fixed at configuration time of the communications network 500. The nodes 506 and links 504 through which a user-switched, or non-permanent connection, passes, and the channels used for such connection, are determined at connection time of the communications network 500.
From the point of view of a user of the communications network 500, a multiplexer switched data network should be comparable with a black box, which after having been supplied, transfers/transports information without interference from any terminal or computer user. Therefore the resulting connection may be essentially seen as "transparent" which means that the output data from the network is the same as the input data to the network regardless of any transformation of data within the network. In this way, two ends can be matched even though they are different in nature.
An inter-network relationship can be established with other networks, as shown in FIG. 6, where various communications networks have been tied into a multiplexer switcher for communication purposes. The objective of an inter-network relationship is to maintain network independence while at the same time providing a communications path for cooperation between end users located in different networks. Therefore, networks may provide the source, destination or part of the route for a route involving a multiplexer switch.
Composition of a network in a conventional multiplexer switch system is as follows. Referring again to FIG. 5, a communications network has a number of nodes 506 at which traffic is switched between end points 502 of the communications network. Each node 506 contains a number of devices which perform data input and output. A device is a printed circuit board (card or a group of cards) which provides the interface to a number of ends 502 or to a composite link 504. Within a node 506, each device is identified by a unique device number. Each device has one or more channels, each of which can carry data from one end connection across the communications network. A device providing the interface to a number of end points 502 has a channel for each end point 502. When a device provides an interface to a composite link 504, it has a channel for each channel on the composite link 504. The size of a device is the number of channels it contains.
Within a device each channel is identified by a unique number, called its channel number. For each device, the relative channel number starts at one and continues upward, the highest channel number being equal to the size of the device. Each channel is also identified by another number, which is an absolute number that is unique to the node 506. A nodes device map (not shown) consists of a list of all of the devices in the node 506, together with their sizes and the absolute channel numbers of their channels. When a connection between two end points 502 of the communications network passes through a node 506, the two channels by which it enters and leaves the node 506 are connected to each other.
The path connections taking place over the communications network 500 are defined by the routing map (not shown). There is a routing map in each node 506, which routing map shows which devices may be used to carry user switch connections to other entities in the communications network 500. A list of pipes is given (a pipe is a set of links 504 that are defined by the user at configuration time). At run time, connections to the destination node are assigned to the devices of the pipes in the routing map, using the first on the list of preferences, and then the second, and so on.
A physical description of a node 506 is shown in FIG. 7 and in FIG. 8. The physical description of a node 506 is the inventory of all its components and their arrangement in relationship to each other. Specifically, a node 506 comprises a master bay 802, and one or more expansion bays 804 (if present) as extensions. For any one node 506, there is a minimum set of cards required inserted into slots 702 of the master bay 802 and the expansion bays 804 (if present). Other cards can be added or deleted according to the functionality of the node 506, depending on the user requirements.
Cards are inserted into the slots 702 of either the master bay 802 or the expansion bays 804 depending on the type of card. The range of components of a node 506 is: a rack, a master bay 802, expansion bays 804 and a set of cards.
Representative card types are defined as follows:
1) Node infrastructure cards--such as user switching options, timing and control, bus extension module, bus termination module, system test and configuration, or buffer cards.
2) Node link cards--such as automatic repeat request (ARQ) or composite links cards.
3) Gateway cards--such as a gateway to foreign networks-X.25, or SNA cards.
4) User requirement cards--such as low speed channel (LSC), or protocol conversions cards.
5) Management cards--such as network control and access module, select and monitor a data channel, or event log and information service cards.
A gateway, a link, or a management card is a device, as is any user card. The whole set of channel cards in a node 506 is one device.
Network configuration is the process by which a user's functional description of the communications network 500 in terms of end points 502 and their connectivity potential (user requirements) is mapped into a logical network; a physical network is obtained from the logical network. The initial network configuration task is the process by which an unconfigured communications network is configured from the user's requirements.
The partial network configuration task is a configuration process by which additional functionality requirements are mapped into the communications network with physical and/or logical network constraints. This partial configuration involves adding or modifying the logical network entities currently in use, but may or may not involve adding or modifying the physical network.
Further, as shown in FIG. 5, when nodes 506 proliferate on the communications network 500, it can be readily appreciated that total configuration of a network beginning with the initial engineering stages requires many man hours of planning and deployment. Various engineering economies are involved, including channel costs, channel speed, bandwidth, and the availability, reliability, and number of links. If a communications network is configured inadequately at the beginning, and/or installed based on erroneous information, expenditures required to alleviate the design criteria or deployment errors may be enormous. Further complicating the communications network configuration problem is the inevitable growth of the number of users accessing the communications network.
Network reconfiguration therefore can require tremendous outlays of manpower and resources.
Research shows that the main reasons for (re)configuration are: addition of terminals and/or computer ports (that is, addition of ends 502), addition of nodes 506, changes in user connection requirements, addition of feeders 508, or changes in composite links 504. Every time a reconfiguration occurs, research shows that the first reconfiguration attempt introduces errors which necessitate re-working of the configuration. Without taking into account major network re-configurations, an average of 140 small reconfigurations per year in a network with 20 nodes or more, requires 1.5 man-days per reconfiguration to be implemented on average. Therefore one can readily appreciate the enormous capital outlay required do manage the configuration process for a communications network.
Articles and publications relating to the subject matter of the present invention included the following (which are incorporated herein by reference):
1. Programming Expert Systems in OPS 5--An Introduction to Rule-Based Programming--Lee Brownston, Robert Farrell, Elaine Dant, Nancy Martin--Addison --Wesley Publishing Company Ltd--1985.
2. Principles of Rule-Based Expert Systems--Bruce G. Buchanen, Richard O'Dude--Heunistic Programming Project--Report No HPP-82-14--Stanford University, 1982.
3. Frame-Base Computer Network Monitoring--Lawrence A. Stotile--Proc. AAAI, 1982.
4. Compass: An Expert System For Telephone Switch Maintenance--S K Gayal, D S Preven, A V Lemenon, A Gundesson, R E Reinke--Expert Systems, July 1985, Vol 1, No 3.
5. YES/MVS--A Continuous Monitoring Expert System For Computer Operations--R L Ennis, J H Griesen, S J Hong, M Karnaugh, J K Kastner, D A Klein, D R Milliken, M I Schol, H M Van Woerkom--IBM Jnl. Research & Development, Vol 30, No 1, January 1986.
6. R1: An Expert in the Computer Systems Domain--J McDermouth--Proc. AAAI, 1980.
7. The OPS 5 User's Manual--C L Forgy--Technical Report--Carnegie-Mellon University--Department of Computer Science, 1980.
8. The OPS-83.TM. User's Manual--C L Forgy--Production Systems Technologies Inc, 1985.
9. Artificial Intelligence Prepares For 2001--N J Nilsson--The AI Magazine--Winter 1983.
10. ACE--An Expert System For Telephone Cable Maintenance--G T Vesonder, S J Stofo, J E Zielinster, F D Miller--Proceedings of IJCAI--1983.
11. UNIFY.TM.--Relational Data Base Management System--Reference Manual Release 3.2--Unify Corporation, Inc--1985.
12. DCX--User Guide--Case Communications Ltd., London, England--1985.